Phospholipids are ampiphilic, and can form hydrogen bonds that way. But mostly lipids are hydrophobic, and their tails like to stay together and keep out the polar water molecules. Though the tails are full of hydrogen bonded to carbon, it is not hydrogen bonding that keeps them together. I forgot what the forces are called that keep the hydrophobic parts together. Anybody know?

Did you know that macromolecules according to ACS (chemists) can consist of molecules put together without covalent bonds? If you were to look at a chylomicrons (a huge aggregate of lipids from the diet), you would postulate that they are macromolecules: repeating units of lipids that are held together, not covently bonded, with vander Waals forces. All polymers are macromolecules, but not all macromolecules are polymers.